2013 Annual Science Report

Pennsylvania State University
Reporting | SEP 2012 – AUG 2013

Executive Summary

At the core of Astrobiology and at the forefront of NASA goals is the construction of a fundamental scientific knowledge base that enables the recognition of signatures of life on the early Earth, in extreme environments, and in extraterrestrial settings. PSARC has continued to pursue an interdisciplinary investigation of biosignatures at all scales, from individual cells to the composition of planetary atmospheres. Our pale blue dot provides the only known example of an inhabited planet. Its record of life extends billions of years into the past, and thus presents a rich variety of indicators of life. Over the past year, our research has included advances in the following four directions.

Developing New BiosignaturesSchopf and his collaborators continued to develop Raman imaging of microfossils as a tool for Astrobiology. In particular, they are working on anaerobic microbial sulfuretums of various ages including the ~775 Ma ... Continue reading.

Project Reports

Ohmoto group’s activities during the fifth year of the project have focused on the redox evolution of the Earth, particularly the evolution of an aerobic world and the changing O2 content of the Archean atmosphere and oceans. This question has been pursued mostly by investigations of: (1) the origins of MIF-S; (2) the behaviors of redox sensitive elements (Fe, S, C, U, Mo, Ce etc) in (a) submarine hydrothermal systems and (b) paleosols, mostly from the Pilbara Craton, Western Australia. We have also investigated the connection between the evolution of the atmospheric pCO2 and that of the earth’s biosphere through pre-biotic, anaerobic, pre-plant aerobic, and plant stages.

Our work involves the design, assembly, and release to the public of a tree of life calibrated to geologic time (timetree). It is needed by astrobiologists to help determine the source of biomarkers for the presence of life in the geologic record.

We are working on finding potentially habitable extrasolar planets, using a variety of search techniques, and developing some of the technology necessary to find and characterize low mass extrasolar planets. We also work on modeling and numerical techniques relevant to the problem of identifying extrasolar sites for life, and on some aspects of the prospects for life in the Solar System outside the Earth. The ultimate goal is to find signatures of life on nearby extrasolar planets.

PSARC is investigating microbial life in some of Earth’s most mission-relevant modern ecosystems. These environments include the Dead Sea, the Chesapeake Bay impact structure, methane seeps, ice sheets, and redox-stratified Precambrian ocean analogs. We target environments that, when studied, provide fundamental information that can serve as the basis for future solar system exploration. Combining our expertise in molecular biology, geochemistry, microbiology, and metagenomics, and in collaboration with some of the planet’s most extreme explorers, we are deciphering the microbiology, fossilization processes, and recoverable biosignatures from these mission-relevant environments.

PSARC Ph.D. (now postdoctoral researcher at Caltech) Katherine Dawson published a new paper documenting the anaerobic biodegradation of organic biosignature compounds pristane and phytane. PSARC Ph.D. Daniel Jones (now postdoctoral researcher at U. Minnesota) published a new paper that uses metagenomic data to show how sulfur oxidation in the deep subsurface environments may contribute to the formation of caves and the maintenence of deep subsurface microbial ecosystems. PSARC Ph.D. student Khadouja Harouaka published a new paper that represents some of the first available information about possible Ca isotope biosignatures. Lastly, the Macalady group published a paper showing how ecological models based on available energy resources can be used to predict the distribution of microbial populations in space and time.

The development and experimental testing of potential indicators of life is essential for providing a critical scientific basis for the exploration of life in the cosmos. In microbial cultures, potential new biosignatures can be found among isotopic ratios, elemental compositions, and chemical changes to the growth media. Additionally, life can be detected and investigated in natural systems by directing cutting-edge instrumentation towards the investigation of microbial cells, microbial fossils, and microbial geochemical products. Over the next five years, we will combine our geomicrobiological expertise and on-going field-based environmental investigations with a new generation of instruments capable of revealing diagnostic biosignatures. Our efforts will focus on creating innovative approaches for the analyses of cells and other organic material, finding ways in which metal abundances and isotope systems reflect life, and developing creative approaches for using environmental DNA to study present and past life.

The work by Ramirez concerned updating the absorption coefficients in our 1-D climate model. Harman’s work consisted of developing a 1-D code for modeling hydrodynamic escape of hydrogen from rocky planets.

Kump’s group is investigating the redox history of the planet from a number of perspectives: 1) modern analog work at Green Lake (McClure and Havig); 2) the role of anoxia in the end-Permian extinction (Cui and Loope), and the Great Oxidation Event and its aftermath (Rybacki and Bachan). This involves field work, analysis of core materials, and numerical modeling